Compositions of resin-linear organosiloxane block copolymers

ABSTRACT

A process is disclosed for preparing a resin-linear organosiloxane block copolymer by reacting a silanol terminated linear organosiloxane and an organosiloxane resin containing hydrolyzable groups to form a resin-linear organosiloxane block copolymer. The resulting resin-linear organosiloxane block copolymer is then crosslinked to sufficiently increase the average molecular weight of the resin-ituted organosiloxane block copolymer by at least 50%. The resin-linear organosiloxanes block copolymers prepared by the disclosed process may provide optically solid compositions which may be considered as “reprocessable.”

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage filing under 35 U.S.C. §371 ofPCT Application No. PCT/US13/27980 filed on 27 Feb. 2013, currently,which claims the benefit of U.S. Provisional Patent Application No.61/604,556 filed 29 Feb. 2012 under 35 U.S.C. §119 (e). PCT ApplicationNo. PCT/US13/27980 and U.S. Provisional Patent Application No.61/604,556 are hereby incorporated by reference.

BACKGROUND

Light emitting diodes (LEDs) and solar panels use an encapsulant coatingto protect electronic components from environmental factors. Suchprotective coatings must be optically clear to ensure maximum efficiencyof these devices. Furthermore, these protective coatings must be tough,durable, long lasting, and yet easy to apply. Many of the currentlyavailable coatings, however, lack toughness; are not durable; are notlong-lasting; and/or are not easy to apply. There is therefore acontinuing need to identify protective and/or functional coatings inmany areas of emerging technologies.

SUMMARY

Embodiment 1 relates to a process for preparing an organopolysiloxaneblock copolymer comprising:

-   -   I) reacting        -   a) a linear organosiloxane having the formula            R¹ ₂(OH)SiO(R¹ ₂SiO_(2/2))_(n)Si(OH)R¹ ₂,            R¹ _(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q), or    -    combinations of the two linear organosiloxanes,        -   wherein each R¹, at each occurrence, is independently a C₁            to C₃₀ hydrocarbyl,        -   n is 10 to 400,        -   E is a hydrolyzable group containing at least one carbon            atom, each q is, independently, 1, 2 or 3, and        -   b) an organosiloxane resin comprising at least 80 mole % of            [R²SiO_(3/2)] siloxy units in its formula and 1-30 mole % of            siloxy units containing a Si-E bond where E is a            hydrolyzable group containing at least one carbon atom,            wherein each R², at each occurrence, is independently an            aryl or C₁ to C₂₀ hydrocarbyl,        -   in c) an organic solvent,        -   to form a resin-linear organosiloxane block copolymer;        -   wherein the amounts of a) and b) used in step I) are            selected to provide the resin-linear organosiloxane block            copolymer with 40 to 90 mole % of disiloxy units [R¹            ₂SiO_(2/2)] and 10 to 60 mole % of trisiloxy units            [R²SiO_(3/2)], and        -   wherein at least 95 weight percent of the linear            organosiloxane used in step I) is incorporated into the            resin-linear organosiloxane block copolymer;    -   II) reacting the resin-linear organosiloxane block copolymer        from step I) to crosslink the trisiloxy units of the        resin-linear organosiloxane block copolymer sufficiently to        increase the molecular weight of the resin-linear organosiloxane        block copolymer by at least 50%;    -   III) optionally, further processing the resin-linear        organosiloxane block copolymer; and    -   IV) optionally, removing the organic solvent.

Embodiment 2 relates to the process of Embodiment 1, wherein the furtherprocessing enhances storage stability and/or optical clarity.

Embodiment 3 relates to the process of Embodiment 1, wherein the linearorganosiloxane has the formula:(HO)(CH₃)₂SiO[(CH₃)₂SiO_(2/2))]_(n)Si(CH₃)2OH.

Embodiment 4 relates to the process of Embodiment 1, wherein the linearorganosiloxane has the formula:(HO)(CH₃)(C₆H₅)SiO[(CH₃)(C₆H₅)SiO_(2/2))]_(n)Si(CH₃)(C₆H₅)(OH).

Embodiment 5 relates to the process of Embodiment 1, wherein R² isphenyl or methyl.

Embodiment 6 relates to the process of Embodiment 1, wherein E is anoximo, epoxy, carboxy, amino, or amido group.

Embodiment 7 relates to the process of Embodiment 1, wherein E is(CH₃)(CH₃CH₂)C═N—O— (methylethylketoximyl).

Embodiment 8 relates to the process of Embodiment 1, wherein E isH₃CC(═O)O— (acetoxy).

Embodiment 9 relates to the process of Embodiment 1, wherein step II)further comprises adding an organosilane having the formula R⁵_(q)SiX_(4-q), where R⁵ is a C₁ to C₈ hydrocarbyl or a C₁ to C₈halogen-substituted hydrocarbyl, X is a hydrolyzable group, and q is 0,1, or 2.

Embodiment 10 relates to the process of Embodiment 9, wherein theorganosilane comprises an alkyltriacetoxysilane.

Embodiment 11 relates to the process of Embodiment 10, wherein thealkyltriacetoxysilane comprises a mixture of two alkyltriacetoxysilanes.

Embodiment 12 relates to the process of Embodiment 11, wherein themixture of two alkyltriacetoxysilanes comprises methyltriacetoxysilaneand/or ethyltriacetoxysilane.

Embodiment 13 relates to the process of Embodiment 9, wherein the amountof organosilane added provides a molar stoichiometry of 2 to 15 mole %of organosilane per mole of Si in the organosiloxane resin.

Embodiment 14 relates to the process of Embodiment 9, wherein saidfurther processing comprises reacting the resin-linear organosiloxanefrom step II) with water and removing acetic acid.

Embodiment 15 relates to the process of Embodiment 1, wherein saidfurther processing comprises reacting the resin-linear organosiloxanefrom step II) with an endcapping compound selected from an alcohol,oxime, or trialkylsiloxy compound.

Embodiment 16 relates to the process of Embodiment 1, wherein instead ofor in addition to said further processing, the organosiloxane blockcopolymer from step II) is contacted with a stabilizer or a superbase.

Embodiment 17 relates to an organopolysiloxane block copolymer preparedby the process of Embodiments 1-16.

Embodiment 18 relates to the organopolysiloxane block copolymer ofEmbodiment 17, wherein the organopolysiloxane block copolymer is thereaction product of step II).

Embodiment 19 relates to a composition comprising the organopolysiloxaneblock copolymer of Embodiment 17.

Embodiment 20 relates to the composition of Embodiment 19, which iscurable.

Embodiment 21 relates to the composition of Embodiment 19, which issolid.

Embodiment 22 relates to a cured product of the composition ofEmbodiments 20-21.

Embodiment 23 relates to a solid film composition comprising thecomposition of Embodiments 18-20.

Embodiment 24 relates to the solid film composition of Embodiment 23,wherein the solid composition has an optical transmittance of at least95%.

Embodiment 25 relates to an LED encapsulant comprising the compositionsof Embodiments 18-24.

DESCRIPTION

The present disclosure provides a process for preparing certain “resinlinear” organosiloxane block copolymers, as well as curable and solidcompositions comprising “resin linear” organosiloxane block copolymers.The “resin-linear” organosiloxane block copolymers, curable compositionsand solid compositions derived from these block copolymers offer anadvantage of being “re-processable.” They may also offer one or morebenefits associated with silicones, including hydrophobicity, hightemperature stability, and moisture/UV resistance. Finally, suchresin-linear organopolysiloxanes block copolymers may also providecoatings having optical transmission greater than 95%.

The process for preparing “resin linear” organosiloxane block copolymersof the embodiments comprises:

-   -   I) reacting        -   a) a linear organosiloxane having the formula            R¹ ₂(OH)SiO(R¹ ₂SiO_(2/2))_(n)Si(OH)R¹ ₂,            R¹ _(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q), or    -    combinations of the two linear organosiloxanes,        -   wherein each R¹, at each occurrence, is independently a C₁            to C₃₀ hydrocarbyl,            -   n is 10 to 400,        -   E is a hydrolyzable group containing at least one carbon            atom, each q is, independently, 1, 2 or 3, and    -   b) an organosiloxane resin comprising at least 60 mole % of        [R²SiO_(3/2)] siloxy units in its formula and 1-30 mole % of        siloxy units containing an Si-E bond, where E is a hydrolyzable        group containing at least one carbon atom, and wherein each R²,        at each occurrence, is independently an aryl, a C₁ to C₂₀        hydrocarbyl,    -   in c) an organic solvent,        -   to form a resin-linear organosiloxane block copolymer;        -   wherein the amounts of a) and b) used in step I are selected            to provide the resin-linear organosiloxane block copolymer            with 40 to 90 mole % of disiloxy units [R¹ ₂SiO_(2/2)] and            10 to 60 mole % of trisiloxy units [R²SiO_(3/2)], and        -   wherein at least 95 weight percent of the linear            organosiloxane used in step I is incorporated into the            resin-linear organosiloxane block copolymer;    -   II) reacting the resin-linear organosiloxane block copolymer        from step I) to crosslink the trisiloxy units of the        resin-linear organosiloxane block copolymer sufficiently to        increase the molecular weight of the resin-linear organosiloxane        block copolymer by at least 50%;    -   III) optionally further processing the resin-linear        organosiloxane block copolymer from step II) to enhance storage        stability and/or optical clarity and/or optionally adding to the        resin-linear organosiloxane block copolymer from step II) a        stabilizer or a superbase; and    -   IV) optionally, removing the organic solvent.

The organopolysiloxanes of the embodiments described herein as“resin-linear” organosiloxane block copolymers. Organopolysiloxanes arepolymers containing siloxy units independently selected from[R₃SiO_(1/2)], [R₂SiO_(2/2)], [RSiO_(3/2)], or [SiO_(4/2)] siloxy units,where R may be, e.g., an organic group. These siloxy units are commonlyreferred to as M, D, T, and Q units respectively. These siloxy units canbe combined in various manners to form cyclic, linear, or branchedstructures. The chemical and physical properties of the resultingpolymeric structures vary depending on the number and type of siloxyunits in the organopolysiloxane. For example, “linear”organopolysiloxanes may contain mostly D, or [R₂SiO_(2/2)] siloxy units,which results in polydiorganosiloxanes that are fluids of varyingviscosities, depending on the “degree of polymerization” or “dp” asindicated by the number of D units in the polydiorganosiloxane. “Linear”organopolysiloxanes may have glass transition temperatures (T_(g)) thatare lower than 25° C. “Resin” organopolysiloxanes result when a majorityof the siloxy units are selected from T or Q siloxy units. When T siloxyunits are predominately used to prepare an organopolysiloxane, theresulting organosiloxane is often referred to as a “resin” or a“silsesquioxane resin.” Increasing the amount of T or Q siloxy units inan organopolysiloxane may result in polymers having increasing hardnessand/or glass like properties. “Resin” organopolysiloxanes thus havehigher T_(g) values, for example siloxane resins often have T_(g) valuesgreater than 40° C., e.g., greater than 50° C., greater than 60° C.,greater than 70° C., greater than 80° C., greater than 90° C. or greaterthan 100° C. In some embodiments, T_(g) for siloxane resins is fromabout 60° C. to about 100° C., e.g., from about 60° C. to about 80° C.,from about 50° C. to about 100° C., from about 50° C. to about 80° C. orfrom about 70° C. to about 100° C.

As used herein “organosiloxane block copolymers” or “resin-linearorganosiloxane block copolymers” refer to organopolysiloxanes containing“linear” D siloxy units in combination with “resin” T siloxy units. Insome embodiments, the organosiloxane copolymers are “block” copolymers,as opposed to “random” copolymers. As such, the “resin-linearorganosiloxane block copolymers” of the disclosed embodiments refer toorganopolysiloxanes containing D and T siloxy units, where the D units(i.e., [R¹ ₂SiO_(2/2)] units) are primarily bonded together to formpolymeric chains having, in some embodiments, an average of from 10 to400 D units (e.g., an average of from about 10 to about 350 D units;about 10 to about 300 D units; about 10 to about 200 D units; about 10to about 100 D units; about 50 to about 400 D units; about 100 to about400 D units; about 150 to about 400 D units; about 200 to about 400 Dunits; about 300 to about 400 D units; about 50 to about 300 D units;about 100 to about 300 D units; about 150 to about 300 D units; about200 to about 300 D units; about 100 to about 150 D units, about 115 toabout 125 D units, about 90 to about 170 D units or about 110 to about140 D units), which are referred herein as “linear blocks.”

The T units (i.e., [R²SiO_(3/2)]) are, in some embodiments, primarilybonded to each other to form branched polymeric chains, which arereferred to as “non-linear blocks.” In some embodiments, a significantnumber of these non-linear blocks may further aggregate to form“nano-domains” when solid forms of the block copolymer are provided. Insome embodiments, these nano-domains form a phase separate from a phaseformed from linear blocks having D units, such that a resin-rich phaseforms.

In some embodiments, the non-linear blocks have a number averagemolecular weight of at least 500 g/mole, e.g., at least 1000 g/mole, atleast 2000 g/mole, at least 3000 g/mole or at least 4000 g/mole; or havea molecular weight of from about 500 g/mole to about 4000 g/mole, fromabout 500 g/mole to about 3000 g/mole, from about 500 g/mole to about2000 g/mole, from about 500 g/mole to about 1000 g/mole, from about 1000g/mole to 2000 g/mole, from about 1000 g/mole to about 1500 g/mole, fromabout 1000 g/mole to about 1200 g/mole, from about 1000 g/mole to 3000g/mole, from about 1000 g/mole to about 2500 g/mole, from about 1000g/mole to about 4000 g/mole, from about 2000 g/mole to about 3000 g/moleor from about 2000 g/mole to about 4000 g/mole.

The organosiloxane block copolymers (e.g., those comprising 40 to 90mole percent disiloxy units of the formula [R¹ ₂SiO_(2/2)] and 10 to 60mole percent trisiloxy units of the formula [R²SiO_(3/2)]) may berepresented by the formula [R¹ ₂SiO_(2/2)]_(a)[R²SiO_(3/2)]_(b) wherethe subscripts a and b represent the mole fractions of the siloxy unitsin the copolymer,

-   -   a is about 0.4 to about 0.9,        -   alternatively from about 0.5 to about 0.9,            -   alternatively about 0.6 to about 0.9,    -   b is from 0.1 to 0.6,        -   alternatively about 0.1 to about 0.5,            -   alternatively about 0.1 to about 0.4,    -   wherein each R¹, at each occurrence, is independently a C₁ to        C₃₀ hydrocarbyl, and    -   each R², at each occurrence, is independently a C₁ to C₂₀        hydrocarbyl.

In some embodiments, the organosiloxane block copolymers of theembodiments described herein comprise 40 to 90 mole percent disiloxyunits of the formula [R¹ ₂SiO_(2/2)], e.g., 50 to 90 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 60 to 90 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 65 to 90 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 70 to 90 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; or 80 to 90 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 80 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 70 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 60 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 50 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 50 to 80 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 50 to 70 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 50 to 60 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 60 to 80 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; 60 to 70 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)]; or 70 to 80 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)].

In some embodiments, the organosiloxane block copolymers of theembodiments described herein comprise 10 to 60 mole percent trisiloxyunits of the formula [R²SiO_(3/2)], e.g., 10 to 20 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 10 to 30 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 10 to 35 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 10 to 40 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 10 to 50 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 20 to 30 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 20 to 35 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 20 to 40 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 20 to 50 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 20 to 60 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 30 to 40 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 30 to 50 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 30 to 60 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; 40 to 50 mole percenttrisiloxy units of the formula [R²SiO_(3/2)]; or 40 to 60 mole percenttrisiloxy units of the formula [R²SiO_(3/2)].

It should be understood that the organosiloxane block copolymers of theembodiments described herein may contain additional siloxy units, suchas M siloxy units, Q siloxy units, other unique D or T siloxy units (forexample having organic groups other than R¹ or R²), provided that theorganosiloxane block copolymer contains the mole fractions of thedisiloxy and trisiloxy units as described herein. In other words, thesum of the mole fractions as designated by subscripts a and b, do notnecessarily have to sum to one. The sum of a+b may be less than one toaccount for minor amounts of other siloxy units that may be present inthe organosiloxane block copolymer. Alternatively, the sum of a+b isgreater than 0.6, alternatively greater than 0.7, alternatively greaterthan 0.8, or alternatively greater than 0.9. In some embodiments, thesum of a+b is from about 0.6 to about 0.9, e.g., from about 0.6 to about0.8, from about 0.6 to about 0.7, from about 0.7 to about 0.9, fromabout 0.7 to about 0.8, or from about 0.8 to about 0.9.

In one embodiment, the organosiloxane block copolymer consistsessentially of the disiloxy units of the formula [R¹ ₂SiO_(2/2)] andtrisiloxy units of the formula [R²SiO_(3/2)], while also containing 0.5to 25 mole percent silanol groups [≡SiOH] (e.g., 0.5 to 5 mole percent,0.5 to 10 mole percent, 0.5 to 15 mole percent, 0.5 to 20 mole percent,5 to 10 mole percent, 5 to 15 mole percent, 5 to 20 mole percent, 5 to25 mole percent, 10 to 15 mole percent 10 to 20 mole percent, 10 to 25mole percent, 15 to 20 mole percent, 15 to 25 mole percent, or 20 to 25mole percent), where R¹ and R² are as defined herein. Thus, in someembodiments, the sum of a+b (when using mole fractions to represent theamount of disiloxy and trisiloxy units in the copolymer) is greater than0.95, alternatively greater than 0.98.

In some embodiments, the resin-linear organosiloxane block copolymersmay also contain from 0.5 to 35 mole percent silanol groups [SiOH],alternatively from 2 to 32 mole percent silanol groups [SiOH], andalternatively from 8 to 22 mole percent silanol groups [SiOH].

The silanol groups may be present on any siloxy units within theorganosiloxane block copolymer. The amount described herein representthe total amount of silanol groups found in the organosiloxane blockcopolymer. In some embodiments, the majority (e.g., greater than 75%,greater than 80%, greater than 90%; from about 75% to about 90%, fromabout 80% to about 90%, or from about 75% to about 85%) of the silanolgroups may reside on the trisiloxy units, i.e., the resin component ofthe block copolymer. Although not wishing to be bound by any theory, thesilanol groups present on the resin component of the organosiloxaneblock copolymer allows for the block copolymer to further react or cureat elevated temperatures.

At each occurrence, each R¹ in the above disiloxy unit is independentlya C₁ to C₃₀ hydrocarbyl, where the hydrocarbyl group may independentlybe an alkyl, aryl, or alkylaryl group. Each R¹, at each occurrence, mayindependently be a C₁ to C₃₀ alkyl group, alternatively each R¹, at eachoccurrence, may independently be a C₁ to C₁₈ alkyl group. Alternatively,at each occurrence, each R¹ may independently be a C₁ to C₆ alkyl groupsuch as methyl, ethyl, propyl, butyl, pentyl, or hexyl. Alternatively,at each occurrence, each R¹ may independently be methyl. Each R¹, ateach occurrence, may independently be an aryl group, such as phenyl,naphthyl or an anthryl group. Alternatively, at each occurrence, each R¹may independently be any combination of the aforementioned alkyl or arylgroups. Alternatively, at each occurrence, each R¹ may independently bephenyl or methyl, such that, in some embodiments, each disiloxy unit mayhave two alkyl groups (e.g., two methyl groups); two aryl groups (e.g.,two phenyl groups); or an alkyl (e.g., methyl) and an aryl group (e.g.,phenyl).

At each occurrence, each R² in the above trisiloxy unit is independentlya C₁ to C₂₀ hydrocarbyl (e.g., C₁ to C₁₀ hydrocarbyl), where thehydrocarbyl group may independently be an alkyl, aryl, or alkylarylgroup. Each R², at each occurrence, may independently be a C₁ to C₂₀(e.g., C₁ to C₁₀ hydrocarbyl)alkyl group, alternatively each R², at eachoccurrence, may independently be a C₁ to C₈ alkyl group. Alternatively,at each occurrence, each R² may independently be a C₁ to C₆ alkyl groupsuch as methyl, ethyl, propyl, butyl, pentyl, or hexyl. Alternatively,at each occurrence, each R² may independently be methyl. Each R², ateach occurrence, may independently be an aryl group, such as phenyl,naphthyl or an anthryl group. Alternatively, at each occurrence, each R²may independently be any combination of the aforementioned alkyl or arylgroups. Alternatively, at each occurrence, each R² may independently bephenyl or methyl, such that, in some embodiments, each disiloxy unit mayhave two alkyl groups (e.g., two methyl groups); two aryl groups (e.g.,two phenyl groups); or an alkyl (e.g., methyl) and an aryl group (e.g.,phenyl).

As used herein, hydrocarbyl also includes substituted hydrocarbyls.“Substituted” as used herein refers broadly to replacement of one ormore of the hydrogen atoms of the group with substituents known to thoseskilled in the art and resulting in a stable compound as describedherein. Examples of suitable substituents include, but are not limitedto, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, alkaryl, hydroxy, alkoxy,aryloxy, carboxy (i.e., CO₂H), carboxyalkyl, carboxyaryl, cyano, nitroand the like. Substituted hydrocarbyl also includes halogen substitutedhydrocarbyls, where the halogen may be fluorine, chlorine, bromine orcombinations thereof.

In some embodiments, fluorinated organosiloxane block copolymer can alsobe prepared via the process described herein, such that the resultingfluorinated organosiloxane block copolymers are the same as thosedescribed in U.S. Provisional Patent Appl. Ser. No. 61/608,732, filedMar. 9, 2012; and PCT Appl. No. PCT/US2013/027904, filed Feb. 27, 2013,the entire disclosures of both of which are incorporated by reference asif fully set forth herein.

The formula [R¹ ₂SiO_(2/2)]_(a)[R²SiO_(3/2)]_(b), and related formulaeusing mole fractions, as used herein to describe the organosiloxaneblock copolymers, does not indicate structural ordering of the disiloxy[R¹ ₂SiO_(2/2)] and trisiloxy [R²SiO_(3/2)] units in the copolymer.Rather, this formula is meant to provide a convenient notation todescribe the relative amounts of the two units in the copolymer, as perthe mole fractions described herein via the subscripts a and b. The molefractions of the various siloxy units in the present organosiloxaneblock copolymers, as well as the silanol content, may be readilydetermined by ²⁹Si NMR techniques.

The organosiloxane block copolymers of the embodiments described hereinhave a weight average molecular weight (M_(w)) of at least 20,000g/mole, alternatively a weight average molecular weight of at least40,000 g/mole, alternatively a weight average molecular weight of atleast 50,000 g/mole, alternatively a weight average molecular weight ofat least 60,000 g/mole, alternatively a weight average molecular weightof at least 70,000 g/mole, or alternatively a weight average molecularweight of at least 80,000 g/mole. In some embodiments, theorganosiloxane block copolymers of the embodiments described herein havea weight average molecular weight (M_(w)) of from about 20,000 g/mole toabout 250,000 g/mole or from about 100,000 g/mole to about 250,000g/mole, alternatively a weight average molecular weight of from about40,000 g/mole to about 100,000 g/mole, alternatively a weight averagemolecular weight of from about 50,000 g/mole to about 100,000 g/mole,alternatively a weight average molecular weight of from about 50,000g/mole to about 80,000 g/mole, alternatively a weight average molecularweight of from about 50,000 g/mole to about 70,000 g/mole, alternativelya weight average molecular weight of from about 50,000 g/mole to about60,000 g/mole. In some embodiments, the organosiloxane block copolymersof the embodiments described herein have a number average molecularweight (M_(n)) of from about 15,000 to about 50,000 g/mole; from about15,000 to about 30,000 g/mole; from about 20,000 to about 30,000 g/mole;or from about 20,000 to about 25,000 g/mole. The average molecularweight may be readily determined using Gel Permeation Chromatography(GPC) techniques.

In some embodiments, the structural ordering of the disiloxy andtrisiloxy units may be further described as follows: the disiloxy units[R¹ ₂SiO_(2/2)] are arranged in linear blocks having an average of from10 to 400 disiloxy units [R¹ ₂SiO_(2/2)] per linear block, and thetrisiloxy units [R²SiO_(3/2)] are arranged in non-linear blocks having amolecular weight of at least 500 g/mole. Each linear block is linked toat least one non-linear block in the block copolymer. Furthermore, atleast 30% of the non-linear blocks are crosslinked with each other,alternatively at least at 40% of the non-linear blocks are crosslinkedwith each other, alternatively at least at 50% of the non-linear blocksare crosslinked with each other, wherein all of the percentages givenherein to indicate percent non-linear blocks that are crosslinked are inweight percent.

In other embodiments, from about 30% to about 80% of the non-linearblocks are crosslinked with each other; from about 30% to about 70% ofthe non-linear blocks are crosslinked with each other; from about 30% toabout 60% of the non-linear blocks are crosslinked with each other; fromabout 30% to about 50% of the non-linear blocks are crosslinked witheach other; from about 30% to about 40% of the non-linear blocks arecrosslinked with each other; from about 40% to about 80% of thenon-linear blocks are crosslinked with each other; from about 40% toabout 70% of the non-linear blocks are crosslinked with each other; fromabout 40% to about 60% of the non-linear blocks are crosslinked witheach other; from about 40% to about 50% of the non-linear blocks arecrosslinked with each other; from about 50% to about 80% of thenon-linear blocks are crosslinked with each other; from about 50% toabout 70% of the non-linear blocks are crosslinked with each other; fromabout 50% to about 60% of the non-linear blocks are crosslinked witheach other; from about 60% to about 80% of the non-linear blocks arecrosslinked with each other; or from about 60% to about 70% of thenon-linear blocks are crosslinked with each other.

The crosslinking of the non-linear blocks may be accomplished via avariety of chemical mechanisms and/or moieties. For example,crosslinking of non-linear blocks within the block copolymer may resultfrom the condensation of residual silanol groups present in thenon-linear blocks of the copolymer. Crosslinking of the non-linearblocks within the block copolymer may also occur between “free resin”components and the non-linear blocks. “Free resin” components may bepresent in the block copolymer compositions as a result of using anexcess amount of an organosiloxane resin during the preparation of theblock copolymer. The free resin component may crosslink with thenon-linear blocks by condensation of the residual silanol groups presenton the non-linear and on the free resin. The free resin may providecrosslinking by reacting with lower molecular weight compounds added ascrosslinkers, as described herein. The free resin, when present, may bepresent in an amount of from about 10% to about 20% by weight of theorganosiloxane block copolymers of the embodiments described herein,e.g., from about 15% to about 20% by weight organosiloxane blockcopolymers of the embodiments described herein.

In some embodiments, certain compounds may be added during thepreparation of the block copolymer, e.g., as crosslinkers. Thesecompounds may include an organosilane having the formula R⁵_(q)SiX_(4-q), which is added during the formation of the blockcopolymer (step II as discussed herein), where R⁵ is a C₁ to C₈hydrocarbyl or a C₁ to C₈ halogen-substituted hydrocarbyl; X is ahydrolyzable group; and q is 0, 1, or 2. R⁵ is a C₁ to C₈ hydrocarbyl ora C₁ to C₈ halogen-substituted hydrocarbyl, or alternatively R⁵ is a C₁to C₈ alkyl group, or alternatively a phenyl group, or alternatively R⁵is methyl, ethyl, or a combination of methyl and ethyl. X is anyhydrolyzable group, E or, alternatively, X may be an oximo, acetoxy,halogen atom, hydroxyl (OH), or an alkoxy group.

In one embodiment, the organosilane having the formula R⁵ _(q)SiX_(4-q)is an alkyltriacetoxysilane, such as methyltriacetoxysilane,ethyltriacetoxysilane, or a combination of both. Commercially availablerepresentative alkyltriacetoxysilanes include ETS-900 (Dow CorningCorp., Midland, Mich.).

The amount of organosilane having the formula R⁵ _(q)SiX_(4-q) whenadded during step II) may vary, but, in some embodiments, is based onthe amount of organosiloxane resin used in the process. For example, theamount of silane used may provide a molar stoichiometry of 2 to 15 mole% of organosilane/moles of Si in the organosiloxane resin, e.g., 2 to 10mole % of organosilane/moles of Si in the organosiloxane resin; 5 to 15mole % of organosilane/moles of Si in the organosiloxane resin; 2 to 5mole % of organosilane/moles of Si in the organosiloxane resin; 10 to 15mole % of organosilane/moles of Si in the organosiloxane resin; 5 to 10mole % of organosilane/moles of Si in the organosiloxane resin; or 2 to12 mole % of organosilane/moles of Si in the organosiloxane resin.Furthermore, the amount of the organosilane having the formula R⁵_(q)SiX_(4-q) added during step II) is, in some embodiments, controlledto ensure a stoichiometry that does not consume all the silanol groupson the organosiloxane block copolymer. In one embodiment, the amount ofthe organosilane used in step II) is selected to provide anorganosiloxane block copolymer containing 0.5 to 35 mole percent ofsilanol groups [≡SiOH].

Other suitable, non-limiting organosilanes useful, e.g., as crosslinkersinclude; methyl tris(methylethylketoxime)silane (MTO), methyltriacetoxysilane, ethyl triacetoxysilane, tetraacetoxysilane,tetraoximesilane, dimethyl diacetoxysilane, dimethyl dioximesilane, andmethyl tris(methylmethylketoxime) silane.

The crosslinks within the block copolymer may primarily be siloxanebonds, ≡Si—O—Si≡, resulting from the condensation of silanol groups, asdiscussed herein.

The amount of crosslinking in the block copolymer may be estimated bydetermining the average molecular weight of the block copolymer, such aswith GPC techniques. In some embodiments, crosslinking the blockcopolymer increases its average molecular weight. Thus, an estimation ofthe extent of crosslinking may be made, given the average molecularweight of the block copolymer, the selection of the linear siloxycomponent (that is the chain length as indicated by its degree ofpolymerization), and the molecular weight of the non-linear block (whichis primarily controlled by the selection of the organosiloxane resinused to prepare the block copolymer).

In some embodiments, solid compositions, which include a resin-linearorganosiloxane block copolymer of some of the embodiments describedherein, also contain a superbase catalyst. See, e.g., PCT Appl. No.PCT/US2012/069701, filed Dec. 14, 2012; and U.S. Provisional Appl. No.61/570,477, filed Dec. 14, 2012, the entireties of which areincorporated by reference as if fully set forth herein.

In some embodiments, solid compositions, which include a resin-linearorganosiloxane block copolymer of some of the embodiments describedherein, also contain a stabilizer. See, e.g., PCT Appl. No.PCT/US2012/067334, filed Nov. 30, 2012; and U.S. Provisional Appl. No.61/566,031, filed Dec. 2, 2011, the entireties of which are incorporatedby reference as if fully set forth herein.

The present disclosure further provides curable compositions comprising:

a) the organosiloxane block copolymers as described herein, in someembodiments in combination with a stabilizer or a superbase as describedherein, and

b) an organic solvent.

In some embodiments, the organic solvent is an aromatic solvent, such asbenzene, toluene, xylene, or combinations thereof.

In one embodiment, the curable compositions may further contain anorganosiloxane resin (e.g., free resin that is not part of the blockcopolymer). The organosiloxane resin present in these compositions is,in some embodiments, the same organosiloxane resin used to prepare theorganosiloxane block copolymer. Thus, the organosiloxane resin maycomprise at least 60 mole % of [R²SiO_(3/2)] siloxy units in its formula(e.g., at least 70 mole % of [R²SiO_(3/2)] siloxy units or at least 80mole % of [R²SiO_(3/2)] siloxy units; or 60-70 mole % [R²SiO_(3/2)]siloxy units, 60-80 mole % [R²SiO_(3/2)] siloxy units or 70-80 mole %[R²SiO_(3/2)] siloxy units), wherein each R², at each occurrence, isindependently a C₁ to C₂₀ hydrocarbyl. Alternatively, the organosiloxaneresin is a silsesquioxane resin, or alternatively a phenylsilsesquioxane resin.

The amount of the organosiloxane block copolymers, organic solvent, andoptional organosiloxane resin in a curable composition may vary. Acurable composition may contain:

-   -   40 to 80 weight % of the organosiloxane block copolymer as        described herein (e.g., 40 to 70 weight %, 40 to 60 weight %, 40        to 50 weight %);    -   10 to 80 weight % of the organic solvent (e.g., 10 to 70 weight        %, 10 to 60 weight %, 10 to 50 weight %, 10 to 40 weight %, 10        to 30 weight %, 10 to 20 weight %, 20 to 80 weight %, 30 to 80        weight %, 40 to 80 weight %, 50 to 80 weight %, 60 to 80 weight        %, or 70 to 80 weight); and    -   5 to 40 weight % of the organosiloxane resin (e.g., 5 to 30        weight %, 5 to 20 weight %, 5 to 10 weight %, 10 to 40 weight %,        10 to 30 weight %, 10 to 20 weight %, 20 to 40 weight % or 30 to        40 weight %);        such that the sum of the weight % of these components does not        exceed 100%. In one embodiment, curable compositions consist        essentially of the organosiloxane block copolymer as described        herein, the organic solvent, and the organosiloxane resin. In        some embodiments, the weight % of these components sum to 100%,        or nearly 100%.

In yet another embodiment, curable compositions contain a cure catalyst.The cure catalyst may be selected from any catalyst known in the art toeffect condensation cure of organosiloxanes, such as various tin ortitanium catalysts. Condensation catalyst can be any condensationcatalyst that may be used to promote condensation of silicon bondedhydroxy (=silanol) groups to form Si—O—Si linkages. Examples include,but are not limited to, amines and complexes of lead, tin, titanium,zinc, and iron. Other examples include, but are not limited to basiccompounds, such as trimethylbenzylammonium hydroxide,tetramethylammonium hydroxide, n-hexylamine, tributylamine,diazabicycloundecene (DBU) and dicyandiamide; and metal-containingcompounds such as tetraisopropyl titanate, tetrabutyl titanate, titaniumacetylacetonate, aluminum triisobutoxide, aluminum triisopropoxide,zirconium tetra(acetylacetonato), zirconium tetrabutylate, cobaltoctylate, cobalt acetylacetonato, iron acetylacetonato, tinacetylacetonato, dibutyltin octylate, dibutyltin laurate, zinc octylate,zinc bezoate, zinc p-tert-butylbenzoate, zinc laurate, zinc stearate,aluminium phosphate, and alminium triisopropoxide; organic titaniumchelates such as aluminium trisacetylacetonate, aluminiumbisethylacetoacetate monoacetylacetonate,diisopropoxybis(ethylacetoacetate)titanium, anddiisopropoxybis(ethylacetoacetate)titanium. In some embodiments, thecondensation catalysts include zinc octylate, zinc bezoate, zincp-tert-butylbenzoate, zinc laurate, zinc stearate, aluminium phosphate,and aluminum triisopropoxide. See, e.g., U.S. Pat. No. 8,193,269, theentire disclosure of which is incorporated by reference as if fully setforth herein. Other examples of condensation catalysts include, but arenot limited to aluminum alkoxides, antimony alkoxides, barium alkoxides,boron alkoxides, calcium alkoxides, cerium alkoxides, erbium alkoxides,gallium alkoxides, silicon alkoxides, germanium alkoxides, hafniumalkoxides, indium alkoxides, iron alkoxides, lanthanum alkoxides,magnesium alkoxides, neodymium alkoxides, samarium alkoxides, strontiumalkoxides, tantalum alkoxides, titanium alkoxides, tin alkoxides,vanadium alkoxide oxides, yttrium alkoxides, zinc alkoxides, zirconiumalkoxides, titanium or zirconium compounds, especially titanium andzirconium alkoxides, and chelates and oligo- and polycondensates of theabove alkoxides, dialkyltin diacetate, tin(II) octoate, dialkyltindiacylate, dialkyltin oxide and double metal alkoxides. Double metalalkoxides are alkoxides containing two different metals in a particularratio. In some embodiments, the condensation catalysts include titaniumtetraethylate, titanium tetrapropylate, titanium tetraisopropylate,titanium tetrabutylate, titanium tetraisooctylate, titanium isopropylatetristearoylate, titanium truisopropylate stearoylate, titaniumdiisopropylate distearoylate, zirconium tetrapropylate, zirconiumtetraisopropylate, zirconium tetrabutylate. See, e.g., U.S. Pat. No.7,005,460, the entire disclosure of which is incorporated by referenceas if fully set forth herein. In addition, the condensation catalystsinclude titanates, zirconates and hafnates as described in DE 4427528 C2and EP 0 639 622 B1, both of which are incorporated by reference as iffully set forth herein.

Solid compositions containing the resin-linear organosiloxane blockcopolymers may be prepared by removing the solvent from the curableorganosiloxane block copolymer compositions described herein. Thesolvent may be removed by any known processing techniques. In oneembodiment, a film of a curable composition containing theorganosiloxane block copolymers is formed, and the solvent is allowed toevaporate from the film. Subjecting the films to elevated temperatures,and/or reduced pressures, may accelerate solvent removal and subsequentformation of the solid curable composition. Alternatively, the curablecompositions may be passed through an extruder to remove solvent andprovide the solid composition in the form of a ribbon or pellets.Coating operations against a release film could also be used as in slotdie coating, knife over roll, rod, or gravure coating. Also,roll-to-roll coating operations could be used to prepare a solid film.In coating operations, a conveyer oven or other means of heating andevacuating the solution can be used to drive off the solvent and obtainthe final solid film.

Although not wishing to be bound by any theory, it is possible that thestructural ordering of the disiloxy and trisiloxy units in theorganosiloxane block copolymer, as described herein, may provide thecopolymer with certain unique physical property characteristics whensolid compositions of the block copolymer are formed. For example, thestructural ordering of the disiloxy and trisiloxy units in the copolymermay provide solid coatings that allow for a high optical transmittanceof visible light (e.g., at least an 85% transmittance; at least a 90%transmittance; at least a 95% transmittance; at least a 99%transmittance; or 100% transmittance at wavelengths above 350 nm). Thestructural ordering may also allow the organosiloxane block copolymer toflow and cure upon heating, yet remain stable at room temperature. Theymay also be processed using lamination techniques. These properties areuseful to provide coatings for various electronic articles to improveweather resistance and durability, while providing low cost and easyprocedures that are energy efficient.

The present disclosure further relates to solid forms of theaforementioned organosiloxane block copolymers and solid compositionsderived from the curable compositions described herein comprising theorganosiloxane block copolymers. Thus, the present disclosure providesorganosiloxane block copolymers comprising:

40 to 90 mole percent disiloxy units of the formula [R¹ ₂SiO_(2/2)],

10 to 60 mole percent trisiloxy units of the formula [R²SiO_(3/2)],

0.5 to 25 mole percent silanol groups [≡SiOH];

wherein:

-   -   each R¹, at each occurrence, is independently a C₁ to C₃₀        hydrocarbyl,    -   each R², at each occurrence, is independently a C₁ to C₂₀        hydrocarbyl;

wherein:

-   -   the disiloxy units [R¹ ₂SiO_(2/2)] are arranged in linear blocks        having an average of from 10 to 400 disiloxy units [R¹        ₂SiO_(2/2)] per linear block, the trisiloxy units [R²SiO_(3/2)]        are arranged in non-linear blocks having a molecular weight of        at least 500 g/mole, at least 30% of the non-linear blocks are        crosslinked with each other and are predominately aggregated        together in nano-domains,    -   each linear block is linked to at least one non-linear block;        and    -   the organosiloxane block copolymer has a weight average        molecular weight of at least 20,000 g/mole, and is a solid at        25° C.

In some embodiments, the organosiloxane block copolymers contained inthe solid forms and solid compositions comprise 40 to 90 mole percentdisiloxy units of the formula [R¹ ₂SiO_(2/2)], e.g., 50 to 90 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 60 to 90 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 65 to 90 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 70 to 90 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; or 80 to 90 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 80 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 70 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 60 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 40 to 50 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 50 to 80 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 50 to 70 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 50 to 60 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 60 to 80 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; 60 to 70 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)]; or 70 to 80 molepercent disiloxy units of the formula [R¹ ₂SiO_(2/2)].

In some embodiments, the organosiloxane block copolymers contained inthe solid forms and solid compositions comprise 10 to 60 mole percenttrisiloxy units of the formula [R²SiO_(3/2)], e.g., 10 to 20 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 10 to 30 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 10 to 35 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 10 to 40 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 10 to 50 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 20 to 30 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 20 to 35 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 20 to 40 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 20 to 50 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 20 to 60 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 30 to 40 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 30 to 50 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 30 to 60 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; 40 to 50 molepercent trisiloxy units of the formula [R²SiO_(3/2)]; or 40 to 60 molepercent trisiloxy units of the formula [R²SiO_(3/2)].

In some embodiments, the organosiloxane block copolymers contained inthe solid forms and solid compositions comprise 0.5 to 25 mole percentsilanol groups [≡SiOH] (e.g., 0.5 to 5 mole percent, 0.5 to 10 molepercent, 0.5 to 15 mole percent, 0.5 to 20 mole percent, 5 to 10 molepercent, 5 to 15 mole percent, 5 to 20 mole percent, 5 to 25 molepercent, 10 to 15 mole percent 10 to 20 mole percent, 10 to 25 molepercent, 15 to 20 mole percent, 15 to 25 mole percent, or 20 to 25 molepercent).

In some embodiments, the disiloxy units [R¹ ₂SiO_(2/2)] in theorganosiloxane block copolymers contained in the solid forms and solidcompositions are arranged in linear blocks having an average of 10 to400 disiloxy units, e.g., an average of from about 10 to about 350disiloxy units; about 10 to about 300 disiloxy units; about 10 to about200 disiloxy units; about 10 to about 100 disiloxy units; about 50 toabout 400 disiloxy units; about 100 to about 400 disiloxy units; about150 to about 400 disiloxy units; about 200 to about 400 disiloxy units;about 300 to about 400 disiloxy units; about 50 to about 300 disiloxyunits; about 100 to about 300 disiloxy units; about 150 to about 300disiloxy units; about 200 to about 300 disiloxy units; about 100 toabout 150 disiloxy units, about 115 to about 125 disiloxy units, about90 to about 170 disiloxy units or about 110 to about 140 disiloxyunits).

In some embodiments, the non-linear blocks in the organosiloxane blockcopolymers contained in the solid forms and solid compositions have anumber average molecular weight of at least 500 g/mole, e.g., at least1000 g/mole, at least 2000 g/mole, at least 3000 g/mole or at least 4000g/mole; or have a molecular weight of from about 500 g/mole to about4000 g/mole, from about 500 g/mole to about 3000 g/mole, from about 500g/mole to about 2000 g/mole, from about 500 g/mole to about 1000 g/mole,from about 1000 g/mole to 2000 g/mole, from about 1000 g/mole to about1500 g/mole, from about 1000 g/mole to about 1200 g/mole, from about1000 g/mole to 3000 g/mole, from about 1000 g/mole to about 2500 g/mole,from about 1000 g/mole to about 4000 g/mole, from about 2000 g/mole toabout 3000 g/mole or from about 2000 g/mole to about 4000 g/mole.

In some embodiments, at least 30% of the non-linear blocks in theorganosiloxane block copolymers contained in the solid forms and solidcompositions are crosslinked with each other, e.g., at least 40% of thenon-linear blocks are crosslinked with each other; at least 50% of thenon-linear blocks are crosslinked with each other; at least 60% of thenon-linear blocks are crosslinked with each other; at least 70% of thenon-linear blocks are crosslinked with each other; or at least 80% ofthe non-linear blocks are crosslinked with each other. In otherembodiments, from about 30% to about 80% of the non-linear blocks arecrosslinked with each other; from about 30% to about 70% of thenon-linear blocks are crosslinked with each other; from about 30% toabout 60% of the non-linear blocks are crosslinked with each other; fromabout 30% to about 50% of the non-linear blocks are crosslinked witheach other; from about 30% to about 40% of the non-linear blocks arecrosslinked with each other; from about 40% to about 80% of thenon-linear blocks are crosslinked with each other; from about 40% toabout 70% of the non-linear blocks are crosslinked with each other; fromabout 40% to about 60% of the non-linear blocks are crosslinked witheach other; from about 40% to about 50% of the non-linear blocks arecrosslinked with each other; from about 50% to about 80% of thenon-linear blocks are crosslinked with each other; from about 50% toabout 70% of the non-linear blocks are crosslinked with each other; fromabout 55% to about 70% of the non-linear blocks are crosslinked witheach other; from about 50% to about 60% of the non-linear blocks arecrosslinked with each other; from about 60% to about 80% of thenon-linear blocks are crosslinked with each other; or from about 60% toabout 70% of the non-linear blocks are crosslinked with each other.

In some embodiments, the organosiloxane block copolymers contained inthe solid forms and solid compositions have a weight average molecularweight (M_(w)) of at least 20,000 g/mole, alternatively a weight averagemolecular weight of at least 40,000 g/mole, alternatively a weightaverage molecular weight of at least 50,000 g/mole, alternatively aweight average molecular weight of at least 60,000 g/mole, alternativelya weight average molecular weight of at least 70,000 g/mole, oralternatively a weight average molecular weight of at least 80,000g/mole. In some embodiments, the organosiloxane block copolymerscontained in the solid forms and solid compositions have a weightaverage molecular weight (M_(w)) of from about 20,000 g/mole to about250,000 g/mole or from about 100,000 g/mole to about 250,000 g/mole,alternatively a weight average molecular weight of from about 40,000g/mole to about 100,000 g/mole, alternatively a weight average molecularweight of from about 50,000 g/mole to about 100,000 g/mole,alternatively a weight average molecular weight of from about 50,000g/mole to about 80,000 g/mole, alternatively a weight average molecularweight of from about 50,000 g/mole to about 70,000 g/mole, alternativelya weight average molecular weight of from about 50,000 g/mole to about60,000 g/mole. In some embodiments, the organosiloxane block copolymersof the embodiments described herein have a number average molecularweight (M_(n)) of from about 15,000 to about 50,000 g/mole; from about15,000 to about 30,000 g/mole; from about 20,000 to about 30,000 g/mole;or from about 20,000 to about 25,000 g/mole.

In some embodiments, the aforementioned organosiloxane block copolymersare isolated in a solid form, for example by casting films of a solutionof the block copolymer in an organic solvent (e.g., benzene, toluene,xylene or combinations thereof) and allowing the solvent to evaporate.Under these conditions, the aforementioned organosiloxane blockcopolymers can be provided as solutions in an organic solvent containingfrom about 50 wt % to about 80 wt % solids, e.g., from about 60 wt % toabout 80 wt %, from about 70 wt % to about 80 wt % or from about 75 wt %to about 80 wt % solids. In some embodiments, the solvent is toluene. Insome embodiments, such solutions may have a viscosity of from about 1500cSt to about 4000 cSt at 25° C., e.g., from about 1500 cSt to about 3000cSt, from about 2000 cSt to about 4000 cSt or from about 2000 cSt toabout 3000 cSt at 25° C.

Upon drying or forming a solid, the non-linear blocks of the blockcopolymer further aggregate together to form “nano-domains” As usedherein, “predominately aggregated” means the majority (e.g., greaterthan 50%; greater than 60%; greater than 75%, greater than 80%, greaterthan 90%; from about 75% to about 90%, from about 80% to about 90%, orfrom about 75% to about 85%) of the non-linear blocks of theorganosiloxane block copolymer are found in certain regions of the solidcomposition, described herein as “nano-domains.” As used herein,“nano-domains” refers to those phase regions within the solid blockcopolymer compositions that are phase separated within the solid blockcopolymer compositions and possess at least one dimension sized from 1to 100 nanometers. The nano-domains may vary in shape, providing atleast one dimension of the nano-domain is sized from 1 to 100nanometers. Thus, the nano-domains may be regular or irregularly shaped.The nano-domains may be spherically shaped, tubular shaped, and, in someinstances, lamellar shaped.

In a further embodiment, the solid organosiloxane block copolymers asdescribed herein contain a first phase and an incompatible second phase,the first phase containing predominately the disiloxy units [R¹₂SiO_(2/2)] as defined herein, the second phase containing predominatelythe trisiloxy units [R²SiO_(3/2)] as defined herein, the non-linearblocks being sufficiently aggregated into nano-domains which areincompatible with the first phase.

When solid compositions are formed from curable compositions of theorganosiloxane block copolymer, which also contain an organosiloxaneresin, as described herein, the organosiloxane resin may alsopredominately aggregates within the nano-domains.

The structural ordering of the disiloxy and trisiloxy units in the solidblock copolymers of the present disclosure, and characterization of thenano-domains, may be determined explicitly using certain analyticaltechniques such as Transmission Electron Microscopic (TEM) techniques,Atomic Force Microscopy (AFM), Small Angle Neutron Scattering, SmallAngle X-Ray Scattering, and Scanning Electron Microscopy.

Alternatively, the structural ordering of the disiloxy and trisiloxyunits in the block copolymer, and formation of nano-domains, may beimplied by characterizing certain physical properties of coatingsresulting from the present organosiloxane block copolymers. For example,the present organosiloxane copolymers may provide coatings that have anoptical transmittance of visible light greater than 95%. One skilled inthe art recognizes that such optical clarity is possible (other thanrefractive index matching of the two phases) only when visible light isable to pass through such a medium and not be diffracted by particles(or domains as used herein) having a size greater than 150 nanometers.As the particle size, or domains further decreases, the optical claritymay be further improved. Thus, coatings derived from the presentorganosiloxane copolymers may have an optical transmittance of visiblelight of at least 95%, e.g., at least 96%; at least 97%; at least 98%;at least 99%; or 100% transmittance of visible light. As used herein,the term “visible light” includes light with wavelengths above 350 nm.

An advantage of the present resin-linear organopolysiloxanes blockcopolymers is that they can be processed several times, because theprocessing temperature (T_(processing)) is less than the temperaturerequired to finally cure (T_(cure)) the organosiloxane block copolymer,i.e., T_(processing)<T_(cure). However the organosiloxane copolymer maycure and achieve high temperature stability when T_(processing) is takenabove T_(cure). Thus, the present resin-linear organopolysiloxanes blockcopolymers offer a significant advantage of being “re-processable” inconjunction with the benefits that may be associated with silicones,such as; hydrophobicity, high temperature stability, moisture/UVresistance.

In one embodiment, the solid compositions of the organosiloxane blockcopolymers may be considered as “melt processable.” In some embodiments,the solid compositions, such as a coating formed from a film of asolution containing the organosiloxane block copolymers, exhibit fluidbehavior at elevated temperatures, that is upon “melting.” The “meltprocessable” features of the solid compositions of the organosiloxaneblock copolymers may be monitored by measuring the “melt flowtemperature” of the solid compositions, that is when the solidcomposition demonstrates liquid behavior. The melt flow temperature mayspecifically be determined by measuring the storage modulus (G′), lossmodulus (G″) and tan delta (tan δ) as a function of temperature storageusing commercially available instruments. For example, a commercialrheometer (such as TA Instruments' ARES-RDA—with 2KSTD standard flexularpivot spring transducer, with forced convection oven) may be used tomeasure the storage modulus (G′), loss modulus (G″) and tan delta as afunction of temperature. Test specimens (e.g., 8 mm wide, 1 mm thick)may be loaded in between parallel plates and measured using small strainoscillatory rheology while ramping the temperature in a range from 25°C. to 300° C. at 2° C./min (frequency 1 Hz).

In some embodiments, the tan delta=1 is from about 3 to about 5 hours at150° C., e.g., from about 3 to about 5 minutes at 150° C., from about 10to about 15 minutes at 150° C., from about 10 to about 12 minutes at150° C., from about 8 to about 10 minutes at 150° C., from about 30minutes to about 2.5 hours at 150° C., from about 1 hour to about 4hours at 150° C. or from about 2.5 hours to about 5 hours at 150° C.

In a further embodiment, the solid compositions may be characterized ashaving a melt flow temperature ranging from 25° C. to 200° C.,alternatively from 25° C. to 160° C., or alternatively from 50° C. to160° C.

It is believed that the melt processability benefits enables the reflowof solid compositions of the organosiloxane block copolymers arounddevice architectures at temperatures below T_(cure), after an initialcoating or solid is formed on the device. This feature is verybeneficial to encapsulated various electronic devices.

In one embodiment, the solid compositions of the organosiloxane blockcopolymers may be considered as “curable.” In some embodiments, thesolid compositions, such as a coating formed from a film of a solutioncontaining the organosiloxane block copolymers, may undergo furtherphysical property changes by further curing the block copolymer. Asdiscussed herein, the present organosiloxane block copolymers contain acertain amount of silanol groups. It is possible that the presence ofthese silanol groups on the block copolymer permit further reactivity,e.g., a cure mechanism. Upon curing, the physical properties of solidcompositions may be further altered.

Alternatively, the “melt processability,” the extent of cure, and/or therate of cure of the solid compositions of the organosiloxane blockcopolymers may be determined by rheological measurements at varioustemperatures.

The solid compositions containing the organosiloxane block copolymersmay have a storage modulus (G′) at 25° C. ranging from 0.01 MPa to 500MPa and a loss modulus (G″) ranging from 0.001 MPa to 250 MPa,alternatively a storage modulus (G′) at 25° C. ranging from 0.1 MPa to250 MPa and a loss modulus (G″) ranging from 0.01 MPa to 125 MPa,alternatively a storage modulus (G′) at 25° C. ranging from 0.1 MPa to200 MPa and a loss modulus (G″) ranging from 0.01 MPa to 100 MPa.

The solid compositions containing the organosiloxane block copolymersmay have a storage modulus (G′) at 120° C. ranging from 10 Pa to 500,000Pa and a loss modulus (G″) ranging from 10 Pa to 500,000 Pa,alternatively a storage modulus (G′) at 120° C. ranging from 20 Pa to250,000 Pa and a loss modulus (G″) ranging from 20 Pa to 250,000 Pa,alternatively a storage modulus (G′) at 120° C. ranging from 30 Pa to200,000 Pa and a loss modulus (G″) ranging from 30 Pa to 200,000 Pa.

The solid compositions containing the organosiloxane block copolymersmay have a storage modulus (G′) at 200° C. ranging from 10 Pa to 100,000Pa and a loss modulus (G″) ranging from 5 Pa to 80,000 Pa, alternativelya storage modulus (G′) at 200° C. ranging from 20 Pa to 75,000 Pa and aloss modulus (G″) ranging from 10 Pa to 65,000 Pa, alternatively astorage modulus (G′) at 200° C. ranging from 30 Pa to 50,000 Pa and aloss modulus (G″) ranging from 15 Pa to 40,000 Pa.

The solid compositions may be further characterized by certain physicalproperties such as tensile strength and % elongation at break. Thepresent solid compositions derived from the aforementionedorganosiloxane block copolymers may have an initial tensile strengthgreater than 1.0 MPa, alternatively greater than 1.5 MPa, oralternatively greater than 2 MPa. In some embodiments, the solidcompositions may have an initial tensile strength for from 1.0 MPa toabout 10 MPa, e.g., from about 1.5 MPa to about 10 MPa, from about 2 MPato about 10 MPa, from about 5 MPa to about 10 MPa or from about 7 MPa toabout 10 MPa. The present solid compositions derived from theaforementioned organosiloxane block copolymers may have an initial %elongation at break (or rupture) greater than 40%, alternatively greaterthan 50%, or alternatively greater than 75%. In some embodiments, thesolid compositions may have a % elongation at break (or rupture) of fromabout 20% to about 90%, e.g., from about 25% to about 50%, from about20% to about 60%, from about 40% to about 60%, from about 40% to about50%, or from about 75% to about 90%. As used herein, tensile strengthand % elongation at break are measured according to ASTM D412.

The present disclosure further provides a process for preparing certainresin-linear organosiloxane block copolymers comprising:

-   -   I) reacting        -   a) a linear organosiloxane having the formula            R¹ ₂(OH)SiO(R¹ ₂SiO_(2/2))_(n)Si(OH)R¹ ₂,            R¹ _(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q), or    -    combinations of the two linear organosiloxanes,        -   wherein each R¹, at each occurrence, is independently a C₁            to C₃₀ hydrocarbyl,        -   n is 10 to 400,        -   E is a hydrolyzable group containing at least one carbon            atom, each q is, independently, 1, 2 or 3, and    -   b) an organosiloxane resin comprising at least 80 mole % of        [R²SiO_(3/2)] siloxy units in its formula and 1-30 mole % of        siloxy units containing an Si-E bond, where E is a hydrolyzable        group containing at least one carbon atom, and wherein each R²,        at each occurrence, is independently an aryl or a C₁ to C₂₀        hydrocarbyl,    -   in c) an organic solvent,        -   to form a resin-linear organosiloxane block copolymer;        -   wherein the amounts of a) and b) used in step I are selected            to provide the resin-linear organosiloxane block copolymer            with 40 to 90 mole % of disiloxy units [R¹ ₂SiO_(2/2)] and            10 to 60 mole % of trisiloxy units [R²SiO_(3/2)], and        -   wherein at least 95 weight percent of the linear            organosiloxane used in step I is incorporated into the            resin-linear organosiloxane block copolymer;    -   II) reacting the resin-linear organosiloxane block copolymer        from step I) to crosslink the trisiloxy units of the        resin-linear organosiloxane block copolymer sufficiently to        increase the weight average molecular weight (M_(w)) of the        resin-linear organosiloxane block copolymer by at least 50%;    -   III) optionally further processing the resin-linear        organosiloxane block copolymer from step II) to enhance storage        stability and/or optical clarity and/or optionally adding to the        resin-linear organosiloxane block copolymer from step II) a        stabilizer or a superbase; and    -   IV) optionally, removing the organic solvent.

Step I) in the process comprises reacting:

-   -   a) a linear organosiloxane having the formula        R¹ ₂(OH)SiO(R¹ ₂SiO_(2/2))_(n)Si(OH)R¹ ₂,        R¹ _(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q), or    -    combinations of the two linear organosiloxanes,        -   wherein each R¹, at each occurrence, is independently a C₁            to C₃₀ hydrocarbyl,        -   n is 10 to 400,        -   E is a hydrolyzable group containing at least one carbon            atom, each q is, independently, 1, 2 or 3; and    -   b) an organosiloxane resin comprising at least 80 mole % of        [R²SiO_(3/2)] siloxy units in its formula and 1-30 mole % of        siloxy units containing an Si-E bond, where E is a hydrolyzable        group containing at least one carbon atom, and wherein each R²,        at each occurrence, is independently an aryl or a C₁ to C₂₀        hydrocarbyl.

The reaction of step I) of the process may be represented generallyaccording to the following schematic:

where OH groups on the linear organosiloxane are reacted with thehydrolyzable groups (E) on the organosiloxane resin, to form aresin-linear organosiloxane block copolymer and a H-(E) compound. Thereaction in step I may be considered as a condensation reaction betweenthe organosiloxane resin and the linear organosiloxane.The Linear Organosiloxane

Component a) in step I of the process is a linear organosiloxane havingthe formula R¹ ₂(OH)SiO(R¹ ₂SiO_(2/2))_(n)Si(OH)R¹ ₂ or R¹_(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q), wherein each R¹,at each occurrence, is independently a C₁ to C₃₀ hydrocarbyl; thesubscript q is 1, 2 or 3; and the subscript “n” may be considered as thedegree of polymerization (dp) of the linear organosiloxane and may varyfrom 10 to 400 (e.g., an average of from about 10 to about 400 D units;about 10 to about 300 D units; about 10 to about 200 D units; about 10to about 100 D units; about 50 to about 400 D units; about 100 to about400 D units; about 150 to about 400 D units; about 200 to about 400 Dunits; about 300 to about 400 D units; about 50 to about 300 D units;about 100 to about 300 D units; about 150 to about 300 D units; about200 to about 300 D units; about 100 to about 150 D units, about 115 toabout 125 D units, about 90 to about 170 D units or about 110 to about140 D units). While component a) is described as a linear organosiloxanehaving the formula R¹ ₂(OH)SiO(R¹ ₂SiO_(2/2))_(n)Si(OH)R¹ ₂ or R¹_(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q) one skilled in theart recognizes small amount of alternative siloxy units, such a T[R¹SiO_(3/2)] siloxy units, may be incorporated into the linearorganosiloxane of component a). As such, the organosiloxane may beconsidered as being “predominately” linear by having a majority of D (R¹₂SiO_(2/2)) siloxy units. Furthermore, the linear organosiloxane used ascomponent a) may be a combination of several linear organosiloxanes.Still further, the linear organosiloxane used as component a) maycomprise silanol groups. In some embodiments, the linear organosiloxaneused as component a) comprises from about 0.5 to about 5 mole % silanolgroups, e.g., from about 1 mole % to about 3 mole %; from about 1 mole %to about 2 mole % or from about 1 mole % to about 1.5 mole % silanolgroups.

At each occurrence, each R¹ in the above linear organosiloxane isindependently a C₁ to C₃₀ hydrocarbyl, where the hydrocarbyl group mayindependently be an alkyl, aryl, or alkylaryl group. Each R¹, at eachoccurrence, may independently be a C₁ to C₃₀ alkyl group, alternativelyeach R¹, at each occurrence, may independently be a C₁ to C₁₈ alkylgroup. Alternatively, at each occurrence, each R¹ may independently be aC₁ to C₆ alkyl group such as methyl, ethyl, propyl, butyl, pentyl, orhexyl. Alternatively, at each occurrence, each R¹ may independently bemethyl. Each R¹, at each occurrence, may independently be an aryl group,such as phenyl, naphthyl or an anthryl group. Alternatively, at eachoccurrence, each R¹ may independently be any combination of theaforementioned alkyl or aryl groups. Alternatively, at each occurrence,each R¹ may independently be phenyl or methyl, such that, in someembodiments, each disiloxy unit may have two alkyl groups (e.g., twomethyl groups); two aryl groups (e.g., two phenyl groups); or an alkyl(e.g., methyl) and an aryl group (e.g., phenyl).

In some embodiments, the linear organosiloxane has the formula R¹_(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q), wherein each qis, independently, 1, 2 or 3; and E is a hydrolyzable group containingat least one carbon atom (e.g., from one to ten carbon atoms; from oneto five carbon atoms; from one to four carbon atoms; or from one tothree carbon atoms). In some embodiments, E is selected from an oximo,epoxy, carboxy, amino, amido group or combinations thereof.Alternatively, E may have the formula R¹C(═O)O—, R¹ ₂C═N—O—, orR⁴C═N—O—, where R¹ is as defined herein, and R⁴ is hydrocarbyl. In oneembodiment, E is H₃CC(═O)O— (acetoxy). In one embodiment, E is(CH₃)(CH₃CH₂)C═N—O— (methylethylketoximyl).

In one embodiment, the linear organosiloxane has the formula(HO)(CH₃)₂SiO[(CH₃)₂SiO_(2/2))]_(n)Si(CH₃)₂OH, where n is as definedherein.

In one embodiment, the linear organosiloxane has the formula(HO)(CH₃)(C₆H₅)SiO[(CH₃)(C₆H₅)SiO_(2/2))]_(n)Si(CH₃)(C₆H₅)(OH), where nis defined herein.

Processes for preparing linear organosiloxanes suitable as component a)are known.

The Organosiloxane Resin

Component b) in the present process is an organosiloxane resin comprisesat least 60 mole % of [R²SiO_(3/2)] siloxy units in its formula, whereineach R², at each occurrence, is independently a C₁ to C₂₀ hydrocarbyl,and 1-30 mole % (e.g., 1-10 mole %, 1-5 mole %, 5-15 mole %, 15-20 mole%, 20-25 mole %, 25-30 mole %, 5-10 mole %, 10-15 mole %, 10-20 mole %or 20-30 mole %) of siloxy units contain an Si-E bond, where E is ahydrolyzable group containing at least one carbon atom. Theorganosiloxane resin may contain any amount and combination of other M,D, and Q siloxy units, provided the organosiloxane resin contains atleast 70 mole % of [R²SiO_(3/2)] siloxy units, alternatively theorganosiloxane resin contains at least 80 mole % of [R²SiO_(3/2)] siloxyunits, alternatively the organosiloxane resin contains at least 90 mole% of [R²SiO_(3/2)] siloxy units, or alternatively the organosiloxaneresin contains at least 95 mole % of [R²SiO_(3/2)] siloxy units. In someembodiments, the organosiloxane resin contains from about 70 to about100 mole % of [R²SiO_(3/2)] siloxy units, e.g., from about 70 to about95 mole % of [R²SiO_(3/2)] siloxy units, from about 80 to about 95 mole% of [R²SiO_(3/2)] siloxy units or from about 90 to about 95 mole % of[R²SiO_(3/2)] siloxy units. Organosiloxane resins useful as component b)include those known as “silsesquioxane” resins.

At each occurrence, each R² in the above organosiloxane resin isindependently a C₁ to C₂₀ hydrocarbyl (e.g., C₁ to C₁₀ hydrocarbyl),where the hydrocarbyl group may independently be an alkyl, aryl, oralkylaryl group. Each R², at each occurrence, may independently be a C₁to C₂₀ (e.g., C₁ to C₁₀ hydrocarbyl)alkyl group, alternatively each R²,at each occurrence, may independently be a C₁ to C₈ alkyl group.Alternatively, at each occurrence, each R² may independently be a C₁ toC₆ alkyl group such as methyl, ethyl, propyl, butyl, pentyl, or hexyl.Alternatively, at each occurrence, each R² may independently be methyl.Each R², at each occurrence, may independently be an aryl group, such asphenyl, naphthyl or an anthryl group. Alternatively, at each occurrence,each R² may independently be any combination of the aforementioned alkylor aryl groups. Alternatively, at each occurrence, each R² mayindependently be phenyl or methyl, such that, in some embodiments, eachdisiloxy unit may have two alkyl groups (e.g., two methyl groups); twoaryl groups (e.g., two phenyl groups); or an alkyl (e.g., methyl) and anaryl group (e.g., phenyl).

E may be selected from any hydrolyzable group containing at least onecarbon atom (e.g., from one to ten carbon atoms; from one to five carbonatoms; from one to four carbon atoms; or from one to three carbonatoms). In some embodiments, E is selected from an oximo, epoxy,carboxy, amino, amido group or combinations thereof. Alternatively, Emay have the formula R¹C(═O)O—, R¹ ₂C═N—O—, or R⁴C═N—O—, where R¹ is asdefined herein, and R⁴ is hydrocarbyl. In one embodiment, E isH₃CC(═O)O— (acetoxy). In one embodiment, E is (CH₃)(CH₃CH₂)C═N—O—(methylethylketoximyl).

The weight average molecular weight (M_(w)) of the organosiloxane resinis not limiting, but, in some embodiments, ranges from 1000 to 10000, oralternatively 1500 to 5000 g/mole.

Organosiloxane resins containing, e.g., at least 80 mole % of[R²SiO_(3/2)] siloxy units, and methods for preparing them, are known inthe art. They are, in some embodiments, prepared by hydrolyzing anorganosilane having three hydrolyzable groups on the silicon atom, suchas a halogen or alkoxy group in an organic solvent. A representativeexample for the preparation of a silsesquioxane resin may be found inU.S. Pat. No. 5,075,103. Furthermore, many organosiloxane resins areavailable commercially and sold either as a solid (flake or powder), ordissolved in an organic solvent. Suitable, non-limiting, commerciallyavailable organosiloxane resins useful as component b) include; DowCorning® 217 Flake Resin, 233 Flake, 220 Flake, 249 Flake, 255 Flake,Z-6018 Flake (Dow Corning Corporation, Midland Mich.).

In some embodiments, a silanol-containing organosiloxane resincontaining at least 80 mole % of [R²SiO_(3/2)] siloxy units may reactedwith an “endblocking” compound such as an alkyltriacetoxysilane or adialkylketoxime. The stoichiometry of the endblocking reaction may beadjusted such that a sufficient amount of the endblocking compound isadded to react with some, but not all of the silanol groups on theorganosiloxane resin. In some embodiments, the stoichiometry may beadjusted to react with substantially all of the silanol groups on theorganosiloxane resin. In some embodiments, a mole of the endblockingcompound may be used per mole of silanol on the polydiorganosiloxane.Alternatively, a slight molar excess such as 1 to 10% of the endblockingcompound may be used. When necessary, the reaction is conducted underanhydrous conditions to minimize condensation reactions of the silanolpolydiorganosiloxane. In some embodiments, the silanol terminatedpolydiorganosiloxane and the endblocking compound are dissolved in anorganic solvent under anhydrous conditions, and allowed to react at roomtemperature, or at elevated temperatures (up to the boiling point of thesolvent).

One skilled in the art recognizes that organosiloxane resins containingsuch high amounts of [R²SiO_(3/2)] siloxy units may have a certainconcentration of Si—OZ where Z may be hydrogen (i.e., silanol), an alkylgroup (so that OZ is an alkoxy group), or alternatively OZ may also beany of the “E” hydrolyzable groups as described herein. The Si—OZcontent as a mole percentage of all siloxy groups present on theorganosiloxane resin may be readily determined by ²⁹Si NMR. Theconcentration of the OZ groups present on the organosiloxane resin mayvary, as dependent on the mode of preparation, and subsequent treatmentof the resin. In some embodiments, the silanol (Si—OH) content oforganosiloxane resins suitable for use in the present process may have asilanol content of at least 5 mole %, alternatively of at least 10 mole%, alternatively 25 mole %, alternatively 40 mole %, or alternatively 50mole %. In other embodiments, the silanol content is from about 5 mole %to about 60 mole %, e.g., from about 10 mole % to about 60 mole %, fromabout 25 mole % to about 60 mole %, from about 40 mole % to about 60mole %, from about 25 mole % to about 40 mole % or from about 25 mole %to about 50 mole %.

One skilled in the art further recognizes that organosiloxane resinscontaining such high amounts of [R²SiO_(3/2)] siloxy units and silanolcontents may also retain water molecules, especially in high humidityconditions. Thus, it is often beneficial to remove excess water presenton the resin by “drying” the organosiloxane resin prior to reacting instep I). This may be achieved by dissolving the organosiloxane resin inan organic solvent, heating to reflux, and removing water by separationtechniques (for example Dean Stark trap or equivalent process).

The amounts of a) and b) used in the reaction of step I) are selected toprovide the resin-linear organosiloxane block copolymer with 40 to 90mole % of disiloxy units [R¹ ₂SiO_(2/2)] and 10 to 60 mole % oftrisiloxy units [R²SiO_(3/2)]. The mole % of dilsiloxy and trisiloxyunits present in components a) and b) may be readily determined using²⁹Si NMR techniques. The starting mole % then determines the massamounts of components a) and b) used in step I).

In some embodiments, the amount of components a) and b) may be selectedto ensure there is a molar excess of the silanol groups on theorganosiloxane resin versus the amount of linear organosiloxane added.Thus, a sufficient amount of the organosiloxane resin should be addedto, in some embodiments, react with all the linear organosiloxane usedin step I). As such, a molar excess of the organosiloxane resin may beused. The amounts used may be determined by accounting for the moles ofthe organosiloxane resin used per mole of the linear organosiloxane.

As discussed herein, the reaction effected in step I) is a condensationreaction between the hydrolyzable groups of linear organosiloxane withthe silanol groups on the organosiloxane resin. In some embodiments, asufficient amount of silanol groups remains on the resin component ofthe formed resin-linear organosiloxane copolymer to further react instep II) of the present process. In some embodiments, at least 10 mole%, alternatively at least 20 mole %, or alternatively at least 30 mole %silanol remains on the trisiloxy units of the resin-linearorganosiloxane copolymer as produced in step I) of the present process.In some embodiments, from about 10 mole % to about 60 mole %, e.g., fromabout 20 mole % to about 60 mole %, or from about 30 mole % to about 60mole %, remains on the trisiloxy units of the resin-linearorganosiloxane copolymer as produced in step I) of the present process.

The reaction conditions for reacting the aforementioned (a) linearorganosiloxane with the (b) organosiloxane resin are not limited. Insome embodiments, reaction conditions are selected to effect acondensation type reaction between the a) linear organosiloxane and b)organosiloxane resin. Various non-limiting embodiments, and reactionconditions, are described in the Examples herein. In some embodiments,the (a) linear organosiloxane and the (b) organosiloxane resin arereacted at room temperature. In other embodiments, (a) and (b) arereacted at temperatures that exceed room temperature and that range upto about 50, 75, 100, or even up to 150° C. Alternatively, (a) and (b)can be reacted together at reflux of the solvent. In still otherembodiments, (a) and (b) are reacted at temperatures that are below roomtemperature by 5, 10, or even more than 10° C. In still otherembodiments (a) and (b) react for times of 1, 5, 10, 30, 60, 120, or 180minutes, or even longer. In some embodiments, (a) and (b) are reactedunder an inert atmosphere, such as nitrogen or a noble gas.Alternatively, (a) and (b) may be reacted under an atmosphere thatincludes some water vapor and/or oxygen. Moreover, (a) and (b) may bereacted in any size vessel and using any equipment including mixers,vortexers, stirrers, heaters, etc. In other embodiments, (a) and (b) arereacted in one or more organic solvents which may be polar or non-polar.In some embodiments, aromatic solvents such as toluene, xylene, benzene,and the like are utilized. The amount of the organosiloxane resindissolved in the organic solvent may vary, but may be an amount thatminimizes the chain extension of the linear organosiloxane or prematurecondensation of the organosiloxane resin.

The order of addition of components a) and b) may vary. In someembodiments, the linear organosiloxane is added to a solution of theorganosiloxane resin dissolved in the organic solvent. This order ofaddition may enhance the condensation of the hydrolyzable groups on thelinear organosiloxane with the silanol groups on organosiloxane resin,while minimizing chain extension of the linear organosiloxane orpremature condensation of the organosiloxane resin. In otherembodiments, the organosiloxane resin is added to a solution of thelinear organosiloxane dissolved in the organic solvent.

The progress of the reaction in step I), and the formation of theresin-linear organosiloxane block copolymer, may be monitored by variousanalytical techniques, such as GPC, IR, or ²⁹Si NMR. In someembodiments, the reaction in step I) is allowed to continue until atleast 95 weight percent (e.g., at least 96%, at least 97%, at least 98%,at least 99% or 100%) of the linear organosiloxane used in step I) isincorporated into the resin-linear organosiloxane block copolymer.

The second step of the present process involves further reacting theresin-linear organosiloxane block copolymer from step I) to crosslinkthe trisiloxy units of the resin-linear organosiloxane block copolymerto increase the molecular weight of the resin-linear organosiloxaneblock copolymer by at least 50%, alternatively by at least 60%,alternatively by 70%, alternatively by at least 80%, alternatively by atleast 90%, or alternatively by at least 100%. In some embodiments, thesecond step of the present process involves further reacting theresin-linear organosiloxane block copolymer from step I) to crosslinkthe trisiloxy units of the resin-linear organosiloxane block copolymerto increase the molecular weight of the resin-linear organosiloxaneblock copolymer from about 50% to about 100%, e.g., from about 60% toabout 100%, from about 70% to about 100%, from about 80% to about 100%or from about 90% to about 100%.

The reaction of the second step of the process may be representedgenerally according to the following schematic:

It is believed that reaction of step II) crosslinks the trisiloxy blocksof the resin-linear organosiloxane block copolymer formed in step I),which may increase the average molecular weight of the block copolymer.It is also possible that the crosslinking of the trisiloxy blocksprovides the block copolymer with an aggregated concentration oftrisiloxy blocks, which ultimately may help to form “nano-domains” insolid compositions of the block copolymer. In other words, thisaggregated concentration of trisiloxy blocks may phase separate when theblock copolymer is isolated in a solid form such as a film or curedcoating. The aggregated concentration of trisiloxy block within theblock copolymer and subsequent formation of “nano-domains” in the solidcompositions containing the block copolymer, may provide for enhancedoptical clarity of these compositions as well as the other physicalproperty benefits associated with these materials.

The crosslinking reaction in step II) may be accomplished via a varietyof chemical mechanisms and/or moieties. For example, crosslinking ofnon-linear blocks within the block copolymer may result from thecondensation of residual silanol groups present in the non-linear blocksof the copolymer. Crosslinking of the non-linear blocks within the blockcopolymer may also occur between “free resin” components and thenon-linear blocks. “Free resin” components may be present in the blockcopolymer compositions as a result of using an excess amount of anorganosiloxane resin in step I) of the preparation of the blockcopolymer. The free resin component may crosslink with the non-linearblocks by condensation of the residual silanol groups present on thenon-linear blocks and on the free resin. The free resin may providecrosslinking by reacting with lower molecular weight compounds added ascrosslinkers, as described herein.

Step II) of the process may occur simultaneous upon formation of theresin-linear organosiloxane of step I), or involve a separate reactionin which conditions have been modified to effect the step II) reaction.The step II) reaction may occur in the same conditions as step I. Inthis situation, the step II) reaction proceeds as the resin-linearorganosiloxane copolymer is formed. Alternatively, the reactionconditions used for step I) are extended to further the step II)reaction. Alternatively, the reaction conditions may be changed, oradditional ingredients added to effect the step II) reaction.

In some embodiments, the step II) reaction conditions may depend on theselection of the hydrolyzable group (E) used in the starting resinorganosiloxane. When (E) in the resin organosiloxane is an oxime group,it is possible for the step II) reaction to occur under the samereaction conditions as step I). That is, as the resin-linearorganosiloxane copolymer is formed in step I), it may continue to reactvia condensation of the silanol groups present on the resin component tofurther increase the molecular weight of the resin-linear organosiloxanecopolymer. Not wishing to be bound by any theory, it is possible thatwhen (E) is an oximo group, the hydrolyzed oximo group (for examplemethylethylketoxime) resulting from the reaction in step I) may act as acondensation catalyst for the step II) reaction. As such, the step II)reaction may proceed simultaneously under the same conditions for stepI). In other words, as the resin-linear organosiloxane copolymer isformed in step I), it may further react under the same reactionconditions to further increase its molecular weight via a condensationreaction of the silanol groups present on the resin component of thecopolymer. However, when (E) on the resin organosiloxane is an acetoxygroup, the resulting hydrolyzed group (acetic acid), may notsufficiently catalyze the step II) reaction. Thus, in this situation thestep II) reaction may be enhanced with a further component to effectcondensation of the resin components of the resin-linear organosiloxanecopolymer, as described in the embodiment herein.

In one embodiment of the present process, an organosilane having theformula R⁵ _(q)SiX_(4-q) is added during step II), where R⁵ is a C₁ toC₈ hydrocarbyl or a C₁ to C₈ halogen-substituted hydrocarbyl, X is ahydrolyzable group, and q is 0, 1, or 2. R⁵ is a C₁ to C₈ hydrocarbyl ora C₁ to C₈ halogen-substituted hydrocarbyl, or alternatively R⁵ is a C₁to C₈ alkyl group, or alternatively a phenyl group, or alternatively R⁵is methyl, ethyl, or a combination of methyl and ethyl. X is anyhydrolyzable group, alternatively X may be E, as defined herein, ahalogen atom, hydroxyl (OH), or an alkoxy group. In one embodiment, theorganosilane is an alkyltriacetoxysilane, such asmethyltriacetoxysilane, ethyltriacetoxysilane, or a combination of both.Commercially available representative alkyltriacetoxysilanes includeETS-900 (Dow Corning Corp., Midland, Mich.). Other suitable,non-limiting organosilanes useful in some embodiments include;methyl-tris(methylethylketoxime)silane (MTO), methyl triacetoxysilane,ethyl triacetoxysilane, tetraacetoxysilane, tetraoximesilane, dimethyldiacetoxysilane, dimethyl dioximesilane, methyltris(methylmethylketoxime) silane.

The amount of organosilane having the formula R⁵ _(q)SiX_(4-q) whenadded during step II) varies, and may be based on the amount oforganosiloxane resin used in the process. The amount of silane used mayprovide a molar stoichiometry of 2 to 15 mole % of organosilane permoles of Si on the organosiloxane resin, e.g., 2 to 10 mole % oforganosilane/moles of Si on the organosiloxane resin; 5 to 15 mole % oforganosilane/moles of Si on the organosiloxane resin; 2 to 5 mole % oforganosilane/moles of Si on the organosiloxane resin; 10 to 15 mole % oforganosilane/moles of Si on the organosiloxane resin; 5 to 10 mole % oforganosilane/moles of Si on the organosiloxane resin; or 2 to 12 mole %of organosilane/moles of Si on the organosiloxane resin. Furthermore,the amount of the organosilane having the formula R⁵ _(q)SiX_(4-q) addedduring step II) may be controlled, in some embodiments, to ensure astoichiometry that does not consume all the silanol groups on theorganosiloxane block copolymer. In one embodiment, the amount of theorganosilane used in step II may be selected to provide anorganosiloxane block copolymer containing 0.5 to 35 mole percent ofsilanol groups [SiOH].

Step III) in the process is optional, and involves further processingthe resin-linear organosiloxane block copolymer. Further processingincludes, but is not limited to further processing the resin-linearorganosiloxane block copolymer to enhance its storage stability and/oroptical clarity. Thus, as used herein, the phrase “further processing”refers broadly to any further reaction or treatment of the formedresin-linear organosiloxane copolymer to, among other things, enhanceits storage stability, and/or optical clarity. The resin-linearorganosiloxane copolymer as produced in step II) may, for example, stillcontain a significant amount of reactive “OZ” groups (that is ≡SiOZgroups, where Z is as defined herein), and/or X groups (where X isintroduced into the block copolymer when the organosilane having theformula R⁵ _(q)SiX_(4-q) is used in step II)). The OZ groups present onthe resin-linear organosiloxane copolymer at this stage may be silanolgroups that were originally present on the resin component, oralternatively may result from the reaction of the organosilane havingthe formula R⁵ _(q)SiX_(4-q) with silanol groups, when the organosilaneis used in step II). It is possible that such “OZ” or X groups mayfurther react during storage, limiting shelf stability, or diminishingreactivity of the resin-linear organosiloxane copolymer during end-useapplications. Alternatively, further reaction of residual silanol groupsmay further enhance the formation of the resin domains and improve theoptical clarity of the resin-linear organosiloxane copolymer. Thus,optional step III) may be performed to further react OZ or X present onthe organosiloxane block copolymer produced in step II) to improvestorage stability and/or optical clarity. The conditions for step III)may vary, depending on the selection of the linear and resin components,their amounts, and the endcapping compounds used.

In one embodiment of the process, step III) is performed by reacting theresin-linear organosiloxane from step II) with water and removing anysmall molecular compounds formed in the process, such as acetic acid. Insome embodiments, the resin-linear organosiloxane copolymer may beproduced from a resin organosiloxane where E is an acetoxy group, and/oran acetoxy silane is used in step II). Although not wishing to be boundby any theory, it is possible that in some embodiments, the resin-linearorganosiloxane formed in step II) contains a significant quantity ofhydrolyzable Si—O—C(O)CH₃ groups, which may limit the storage stabilityof the resin-linear organosiloxane copolymer. Thus, water may be addedto the resin-linear organosiloxane copolymer formed from step II), whichmay hydrolyze a substantial amount of Si—O—C(O)CH₃ groups to furthercrosslink the trisiloxy units, and eliminate acetic acid. The formedacetic acid, and any excess water, may be removed by known separationtechniques. The amount of water added in some embodiments may vary. Insome embodiments, the amount of water added may be 10 weight %, oralternatively 5 weight % is added per total solids (as based onresin-linear organosiloxane copolymer in the reaction medium).

In one embodiment of the process, step III) is performed by reacting theresin-linear organosiloxane from step II) with an endcapping compound,including endcapping compounds selected from an alcohol, oxime, ortrialkylsiloxy compound. In some embodiments, the resin-linearorganosiloxane copolymer may be produced from a linear organosiloxanewhere E is an oxime group. The endcapping compound may be a C₁-C₂₀alcohol (e.g., C₁-C₂₀ alcohol, C₁-C₁₂ alcohol, C₁-C₁₀ alcohol, C₁-C₆alcohol or C₁-C₄ alcohol) such as methanol, ethanol, propanol, butanol,or others in the series. Alternatively, the alcohol is n-butanol. Theendcapping compound may also be a trialkylsiloxy compound, such astrimethylmethoxysilane or trimethylethoxysilane. The amount ofendcapping compound may vary. In some embodiments, the amount ofendcapping compound may be between 3 and 15 wt % (e.g., 3 to 10 wt %, 5to 15 wt %, 3 to 5 wt %, 10 to 15 wt %, 5 to 10 wt %, or 3 to 12 wt %)with respect to the resin linear organosiloxane block copolymer solidsin the reaction medium.

Optional step III) in the process may, in addition to, or in place of“further processing,” involve contacting the resin-linear organosiloxaneblock copolymer from step II) with a stabilizer or a superbase.

Step IV) of the present process is optional, and involves removing theorganic solvent used in the reactions of steps I) and II). The organicsolvent may be removed by any known techniques. In some embodiments, theorganic solvent may be removed by heating the resin-linearorganosiloxane copolymer compositions at elevated temperature, either atatmospheric conditions or under reduced pressures. In some embodiments,not all of the solvent is removed. In some embodiments, at least 20%, atleast 30%, at least 40%, or at least 50% of the solvent is removed,e.g., at least 60%, at least 70%, at least 75%, at least 80% or at least90% of the solvent is removed. In some embodiments, less than 20% of thesolvent is removed, e.g., less than 15%, less than 10%, less than 5% or0% of the solvent is removed. In other embodiments, from about 20% toabout 100% of the solvent is removed, e.g., from about 30% to about 90%,from about 20% to about 80%, from about 30 to about 60%, from about 50to about 60%, from about 70 to about 80% or from about 50% to about 90%of the solvent is removed.

Some of the embodiments of the present invention relate to opticalassemblies and articles comprising the compositions described hereinsuch as those described in PCT/US2012/071011, filed Dec. 20, 2012;PCT/US2013/021707, filed Jan. 16, 2013; and PCT/US2013/025126, filedFeb. 7, 2013, all of which are incorporated by reference as if fully setforth herein. Accordingly, some embodiments of the present inventionrelate to an LED encapsulant comprising an organosiloxane blockcopolymer described herein.

The term “about,” as used herein, can allow for a degree of variabilityin a value or range, for example, within 10%, within 5%, or within 1% ofa stated value or of a stated limit of a range.

Values expressed in a range format should be interpreted in a flexiblemanner to include not only the numerical values explicitly recited asthe limits of the range, but also to include all the individualnumerical values or sub-ranges encompassed within that range as if eachnumerical value and sub-range were explicitly recited. For example, arange of “about 0.1% to about 5%” or “about 0.1% to 5%” should beinterpreted to include not just about 0.1% to about 5%, but also theindividual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g.,0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range.

Embodiments of the invention described and claimed herein are not to belimited in scope by the specific embodiments herein disclosed, sincethese embodiments are intended as illustration of several aspects of thedisclosure. Any equivalent embodiments are intended to be within thescope of this disclosure. Indeed, various modifications of theembodiments in addition to those shown and described herein will becomeapparent to those skilled in the art from the foregoing description.Such modifications are also intended to fall within the scope of theappended claims.

The Abstract is provided to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims.

EXAMPLES

The following examples are included to demonstrate specific embodimentsof the invention. However, those of skill in the art should, in light ofthe present disclosure, appreciate that many changes can be made in thespecific embodiments which are disclosed and still obtain a like orsimilar result without departing from the spirit and scope of theinvention. All percentages are in wt %. All measurements were conductedat 23° C. unless indicated otherwise.

Characterization Techniques

²⁹Si and ¹³C NMR Spectrometry

NMR samples of resin linear products were prepared by, e.g., weighing ˜3grams of solvent free resin linear (prepared by drying sample overnightat room temperature), 1 g of CDC₃, and 4 grams of 0.04 M Cr(acac)₃solution in CDC₃ into a vial and mixing thoroughly Samples were thentransferred into a silicon-free NMR tube. Spectra were acquired using aVarian Mercury 400 MHz NMR. NMR samples of other materials such as 217Flake and silanol terminated PDMS were prepared by diluting 4 g ofsample into 4 grams of 0.04 M Cr(acac)₃ solution in CDC₃.

¹³C NMR experiments were performed by, e.g., placing samples into 16 mmglass NMR tubes. A 5 mm NMR tube was placed inside the 16 mm tube andfilled with lock solvent. ¹³C DEPT NMR was acquired in 12 or 20 minutesignal averaging blocks. Data was acquired on a Varian Inova NMRspectrometer with a ¹H operational frequency of 400 MHz.

Silanol content of resin linear products was calculated from theintegration values of the T(Ph,OZ) and T(Ph,OZ2) regions in the ²⁹Si NMRspectrum. T(Alkyl) groups were considered fully condensed (assumption)and subtracted from the T(Ph,OZ) region. The T(Alkyl) content wascalculated by multiplying the integration value of D(Me₂) from ²⁹Si NMRby the fraction (moles Si of coupling agent/moles Si of PDMS used in thesynthesis formulation). Isopropoxy from 217 Flake was not subtracted outof the OZ values due to its low concentration. Therefore it was assumedthat total OZ=total OH.

GPC Analysis

Samples were prepared, e.g., in certified THF at 0.5% w/v concentration,filtered with a 0.45 μm PTFE syringe filter, and analyzed againstpolystyrene standards. The relative calibration (3^(rd) order fit) usedfor molecular weight determination was based on 16 polystyrene standardsranging in molecular weights from 580 to 2,320,000 Daltons. Thechromatographic equipment consisted of a Waters 2695 Separations Moduleequipped with a vacuum degasser, a Waters 2410 differentialrefractometer and two (300 mm×7.5 mm) Polymer Laboratories Mixed Ccolumns (molecular weight separation range of 200 to 3,000,000) precededby a guard column. The separation was performed using certified gradeTHF programmed to flow at 1.0 mL/min., injection volume was set at 100μL and columns and detector were heated to 35° C. Data collection was 25minutes and processing was performed using Atlas/Cirrus software.

To determine free resin content, the free resin peak at lower molecularweight was integrated to get the area percent.

Rheology Analysis

A commercially available rheometer from TA Instruments (ARES-RDA with2KSTD standard flexular pivot spring transducer, TA Instruments, NewCastle, Del. 19720) with forced convection oven was used to measure thestorage modulus (G′), loss modulus (G″) and tan delta as a function oftemperature. Test specimens (e.g., 8 mm wide, 1 mm thick) were loaded inbetween parallel plates and measured using small strain oscillatoryrheology while ramping the temperature in a range from 25° C. to 300° C.at 2° C./min (frequency 1 Hz).

To characterize the copolymers, the flow onset was calculated as theinflection temperature in the G′ drop (labeled FLOW), the viscosity at120° C. will be reported as a measure for melt processability and thecure onset was calculated as the inflection temperature in the G′ rise(labeled CURE).

Optical Clarity

Optical clarity was evaluated as the % transmission of light atwavelengths from about 350-1000 nanometers, measured through 1 mm thicksamples of cast sheets of the present compositions. Samples having a %transmittance of at least 95% were considered to be optically clear.

Example 1 Preparation of 45 wt % Ph-T-126 dp PhMe

A 500 mL round bottom flask was loaded with: toluene (59.29 g) and 217flake (72.0 g, 0.527 moles Si). The flask was equipped with athermometer, glass stir shaft with a teflon paddle, and a Dean Starkapparatus attached to a water-cooled condenser. The Dean Stark apparatuswas prefilled with toluene, a nitrogen blanket was applied, and aheating mantle was used for heating.

At room temperature added 50/50 by weight methyl triacetoxy silane(MTA)/ethyl triacetoxy silane (ETA) (12.58 g, 0.0553 moles) was added tothe 217 flake toluene solution. An exotherm was observed, where thetemperature of the reaction mixture increased from 20° C. to 26° C. Thereaction mixture was heated at reflux for 1 hour and 0.34 mL water wasremoved. The reaction mixture was treated with water (15:1 molar ratio,water:MTA/ETA). The following process was repeated twice: cooled to 90°C. and then added deionized (DI) water (14.94 g); then removed water viaazeotropic distillation over 50 minutes (total amount of water removed:35.8 g).

A solution of silanol terminated PhMe siloxane (135.38 g solution=88.00g siloxane, 0.645 moles Si) was capped with 50/50 MTA/ETA (1.88 g,0.00827 moles Si). The silanol terminated PhMe siloxane was prepared ina glove box (same day) under nitrogen by adding 50/50 MTA/ETA to thesiloxane and mixing at room temperature for 1 hour.

A siloxane solution in toluene was added to the 217 flake solution intoluene quickly at 108° C. The reaction mixture was heated at reflux for2 hours and 0.62 mL water was removed. The reaction mixture was treatedwith water (15:1 molar ratio, water:MTA/ETA), cooled to 90° C., and thenDI water was added (17.18 g). The water was removed water via azeotropicdistillation over 1 hour Total amount of water removed: 35.8 g. Some ofthe volatiles (54.2 g) were distilled to increase the solids content.The non-volatile containing (NVC) samples at room temperature wereclear. Thin films were transparent, though the solution was hazy.

The invention claimed is:
 1. A process for preparing anorganopolysiloxane block copolymer comprising: I) reacting a) a linearorganosiloxane having the formulaR¹ ₂(OH)SiO(R¹ ₂SiO_(2/2))_(n)Si(OH)R¹ ₂,R¹ _(3-q)(E)_(q)SiO(R¹ ₂SiO_(2/2))_(n)Si(E)_(q)R¹ _(3-q), or combinations of the two linear organosiloxanes, wherein each R¹, ateach occurrence, is independently a C₁ to C₃₀ hydrocarbyl, n is 10 to400, E is a hydrolyzable group containing at least one carbon atom, eachq is, independently, 1, 2 or 3, and b) an organosiloxane resincomprising at least 80 mole % of [R²SiO_(3/2)] siloxy units in itsformula and 1-30 mole % of siloxy units containing a Si-E bond where Eis a hydrolyzable group containing at least one carbon atom, whereineach R², at each occurrence, is independently an aryl or C₁ to C₂₀hydrocarbyl, in c) an organic solvent, to form a resin-linearorganosiloxane block copolymer; wherein the amounts of a) and b) used instep I) are selected to provide the resin-linear organosiloxane blockcopolymer with 40 to 90 mole % of disiloxy units [R¹ ₂SiO_(2/2)] and 10to 60 mole % of trisiloxy units [R²SiO_(3/2)], and wherein at least 95weight percent of the linear organosiloxane used in step I) isincorporated into the resin-linear organosiloxane block copolymer; II)reacting the resin-linear organosiloxane block copolymer from step I) tocrosslink the trisiloxy units of the resin-linear organosiloxane blockcopolymer sufficiently to increase the molecular weight of theresin-linear organosiloxane block copolymer by at least 50%; III)optionally, further processing the resin-linear organosiloxane blockcopolymer; and IV) optionally, removing the organic solvent.
 2. Theprocess of claim 1, wherein the linear organosiloxane has the formula(HO)(CH₃)₂SiO[(CH₃)₂SiO_(2/2))]_(n)Si(CH₃)₂OH.
 3. The process of claim1, wherein the linear organosiloxane has the formula(HO)(CH₃)(C₆H₅)SiO[(CH₃)(C₆H₅)SiO_(2/2))]_(n)Si(CH₃)(C₆H₅)(OH).
 4. Theprocess of claim 1, wherein R² is phenyl or methyl.
 5. The process ofclaim 1, wherein E is an oximo, epoxy, carboxy, amino, or amido group.6. The process of claim 1, wherein E is(CH₃)(CH₃CH₂)C═N—O-(methylethylketoximyl).
 7. The process of claim 1,wherein E is H₃CC(═O)O-(acetoxy).
 8. The process of claim 1, whereinstep II) further comprises adding an organosilane having the formula R⁵_(q)SiX_(4-q), where R⁵ is a C₁ to C₈ hydrocarbyl or a C₁ to C₈halogen-substituted hydrocarbyl, X is a hydrolyzable group, and q is 0,1, or
 2. 9. The process of claim 8, wherein the organosilane is analkyltriacetoxysilane.
 10. The process of claim 9, wherein thealkyltriacetoxysilane is a mixture of two alkyltriacetoxysilanes. 11.The process of claim 10, wherein the mixture of twoalkyltriacetoxysilanes comprises methyltriacetoxysilane and/orethyltriacetoxysilane.
 12. The process of claim 8, wherein the amount oforganosilane added provides a molar stoichiometry of 2 to 15 mole % oforganosilane per mole of Si in the organosiloxane resin.
 13. The processof claim 8, wherein said further processing comprises reacting theresin-linear organosiloxane from step II) with an endcapping compoundselected from an alcohol, oxime, or trialkylsiloxy compound.
 14. Theorganopolysiloxane block copolymer prepared by the method of claim 1.15. The organopolyxiloxane block copolymer of claim 14, wherein theorganopolysiloxane block copolymer is the reaction product of step II).16. A solid, curable composition comprising the organopolysiloxane blockcopolymer of claim
 14. 17. The cured product of the composition of claim16.
 18. A solid film composition comprising the composition of claim 16.19. The solid film composition of claim 18, wherein the solidcomposition has an optical transmittance of at least 95%.
 20. An LEDencapsulant comprising the compositions of claim 16.